RESUMO
Treatment of environmental samples under field conditions may require the application of chemical preservatives, although their use sometimes produces changes in the microbial communities. Sodium azide, a commonly used preservative, is known to differentially affect the growth of bacteria. Application of azide and darkness incubation to Isabel soda lake water samples induced changes in the structure of the bacterial community, as assessed by partial 16S rRNA gene pyrosequencing. Untreated water samples (WU) were dominated by gammaproteobacterial sequences accounting for 86%, while in the azide-treated (WA) samples, this group was reduced to 33% abundance, and cyanobacteria-related sequences became dominant with 53%. Shotgun sequencing and genome recruitment analyses pointed to Halomonas campanensis strain LS21 (genome size 4.07 Mbp) and Synechococcus sp. RS9917 (2.58 Mbp) as the higher recruiting genomes from the sequence reads of WA and WU environmental libraries, respectively, covering nearly the complete genomes. Combined treatment of water samples with sodium azide and darkness has proven effective on the selective enrichment of a cyanobacterial group. This approach may allow the complete (or almost-complete) genome sequencing of Cyanobacteria from metagenomic DNA of different origins, and thus increasing the number of the underrepresented cyanobacterial genomes in the databases.
Assuntos
Cianobactérias/isolamento & purificação , Metagenômica/métodos , Microbiota , Azida Sódica/efeitos adversos , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Cianobactérias/genética , DNA Bacteriano , Microbiologia Ambiental , Inibidores Enzimáticos/efeitos adversos , Genoma Bacteriano , Lagos/microbiologia , Microbiota/genética , SalinidadeRESUMO
In the last decade several new genera have been isolated in alkaline and halophile growth conditions. The studies conducted in the Texcoco Lake soils have shown a generalized microbial adaptation to the specific conditions. In this research work, morphological and phylogenetic characterization of the HN31(22) strain that was isolated from the cited soil is presented. The strain was identified as a Gram-positive halophile and alkaline tolerant bacteria from the Nesterenkonia genus, which uses different substrates in metabolic processes.
Assuntos
Lagos/microbiologia , Micrococcaceae/classificação , Filogenia , Microbiologia do Solo , Álcalis/química , México , Micrococcaceae/isolamento & purificação , Fenótipo , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Cloreto de Sódio/química , Solo/químicaRESUMO
Isabel Lake is a moderate saline soda crater lake located in Isabel Island in the eastern tropical Pacific coast of Mexico. Lake is mainly formed by rainfall and is strongly affected by evaporation and high input of nutrients derived from excretions of a large bird community inhabiting the island. So far, only the island macrobiota has been studied. The knowledge of the prokaryotic biota inhabiting the upper layers of this meromictic lake can give clues for the maintenance of this ecosystem. We assessed the diversity and composition of prokaryotic community in sediments and water of the lake by DGGE profiling, 16S rRNA gene amplicon pyrosequencing, and cultivation techniques. The bacterial community is largely dominated by halophilic and halotolerant microorganisms. Alpha diversity estimations reveal higher value in sediments than in water (P > 0.005). The lake water is dominated by γ-Proteobacteria belonging to four main families where Halomonadaceae presents the highest abundance. Aerobic, phototrophic, and halotolerant prokaryotes such as Cyanobacteria GPIIa, Halomonas, Alcanivorax, Idiomarina, and Cyclobacterium genera are commonly found. However, in sediment samples, Formosa, Muricauda, and Salegentibacter genera corresponding to Flavobacteriaceae family accounted for 15-20 % of the diversity. Heterotrophs like those involved in sulfur cycle, Desulfotignum, Desulfuromonas, Desulfofustis, and Desulfopila, appear to play an important role in sediments. Finally, a collection of aerobic halophilic bacterial isolates was created from these samples; members of the genus Halomonas were predominantly isolated from lake water. This study contributes to state the bacterial diversity present in this particular soda saline crater lake.